The field of this invention generally relates to pyrotechnic initiators, and more particularly to a pyrotechnic system having a number of discrete initiators.
Pyrotechnic initiators are used in a number of different applications. One important use is the inflation of an airbag in a motor vehicle. When a pyrotechnic initiator is ignited, the gas and heat released by the initiator may activate a gas generator, rupture a sealed gas unit, or perform some other work which inflates the airbag. As a safety measure, it is known to provide a number of initiators, rather than a single one, for inflating a single airbag. Each of these initiators contains only a fraction of the pyrotechnic material that would be used with a single initiator. Based on factors such as the speed of the vehicle at the time of impact, a different number of initiators are fired to inflate the airbag. For example, where two initiators are provided, a low-speed impact would trigger the firing of one initiator. A medium-speed impact would trigger the firing of one initiator, then another a millisecond later. A high-speed impact would trigger the simultaneous firing of both initiators to inflate the airbag with maximum force. In this way, the force with which the airbag contacts a person in the motor vehicle is adjusted to better compensate for the force of the accident and minimize the potential for injury resulting from excessive airbag deployment force.
While the use of a multiple-initiator assembly is desirable, manufacturing a multiple-initiator unit is complex and expensive. Typically, one or more finished initiators are installed into a larger assembly, creating a need for multiple initiator presses into a base, multiple individual seals, and multiple crimps and welds. Because a number of parts and steps are required, the chance of incurring a manufacturing error increases, thereby resulting in a larger number of rejected parts.
In addition, an insulator can is typically placed around pyrotechnic material in an initiator. The can protects the pyrotechnic material from exposure to atmospheric humidity and contaminants, and prevents ambient charges or stray currents from inadvertently igniting the pyrotechnic material. While the can is useful, it is an additional component which must be assembled into the initiator, adding to the complexity and cost of assembly of the finished part.
The present invention is directed toward a multi-unit pyrotechnic initiation system.
In an aspect of a preferred embodiment, two or more pyrotechnic initiators are molded in place into a base.
In another aspect of a preferred embodiment, each initiator includes a body overmolded around an igniter, eliminating the need for an insulator can around the pyrotechnic material in the igniter.
In an alternate embodiment, the retainers of two or more pyrotechnic initiators are formed together as part of a unitary substructure.
Further aspects and advantages of the preferred embodiments will appear hereinafter.